Electrical apparatus



Feb. 11, 1930. v R. wlLDER 1,746,977

ELECTRICAL APPARATUS Filed Nov. 6. 1926 Fig. I.

1 DIphenyI oxide VIII/IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII III! IIIIIIIIIIIIIIIIIIIIIIIIA IIIIIIIIIIIIII IIIIIII'IIIIII Hg. 2. 28L26\ T T Fi .3. 34 g 34 35 \rumnrmm- Inventor Lawrence R. Wilder Attorney Patented Feb. 11, 1930 UNITED STATES LAWRENCE R. WILDER, OF YORK, N. Y.

ELECTRICAL APPARATUS Application filed November 6, 1926. Serial No. 146,838.

\ My invention relates to electrical apparatus, and it has particular relation to the insulatlng and COOliIlg means of such apparatus.

It is among the objects of the invention to provide apparatus of the foregoing type, utilizing liquid diphenyl oxide as a cooling and insulating medium, or, in general, a substance that has the high dielectric properties 9 of oil, but, in distinction to oil, does not develop explosive gases or mixtures, is not inflammable, and, furthermore, does not detrimentally affect the solid insulation and the conducting members used in such apparatus.

5 My invention will be best understood from the following specification and drawing, in which Fig. 1 is a sectional view of a circuit breaker embodying the invention; and

Fig. 2 is a circuit diagram of the circuit breaker shown in Fig. 1 illustrating additional features of the invention; and

Fig. 3 is a view similar to Fig. 1, of a transformer embodying the present invention.

' Electrical apparatus that is subjected to high voltages, such as circuit breakers or transformers, is usually enclosed in a vessel that is filled with a liquid, in order to increase the heat capacity of the apparatus and better cool the same, and also in order to place the electrical parts of the apparatus in a medium' that has much higher dielectric strength than air or other gases.

Among the liquids that heretofore seemed available for the cooling and insulating of high-voltage electric apparatus, oil was regarded as the best, inasmuch as it appeared to be the only substance of high dielectric strength that would not affect the solid insulation, such as rubber, cotton, wood, etc., or the metallic conductors necessarily forming part of such apparatus.

For many years, very extensive efforts have been made to avoid the use of oil, inasmuch as it develops, when decomposed under the in-.

fiuence of the heat generated in the apparatus, or by reason of arcing under the oil, gases and fires which have caused much damage to electric central stations using such apparatus.

Electrical circuit breakers have received particular attention in this respect, since the are formed under the oil, between the interrupting contacts, would decompose large quantities of the oil and the resulting hot gases would very often form explosive mixtures, bursting the enclosing tank and destroying not only the apparatus itself, but sometimes putting out of operation entire electrical plants, and interrupting the supply of electric current to the territory which is served by the stations.

So important is the problem of avoiding the formation of explosive mixtures and fires in apparatus of the foregoing type, that serious consideration was given to the use of carbon tetrachloride as a substitute for oil; but practical experience has shown that while carbon tetrachloride does not form explosive gas mixtures, it, on the other hand, quickly produces deterioration of the insulation, such as rubber, cotton, wood or otherorganic materials within the apparatus which constitute essential parts of the apparatus. As a result of such deterioration, the expensive apparatus will soon fail in service and have to be replaced.

In accordance with the present invention, I utilize as an insulating or cooling medium, a substance that avoids the difiiculties inherent in the use of oil, as far as. fire hazard and formation of explosive mixtures are concerned and that, on the other hand, is inert with respect to the insulating andconducting mate-' rials, from which the electric apparatus is built.

I have found that liquid diphenyl oxide, (C H,) O, has properties which make it admirably suited for use as an insulating and cooling medium in electric apparatus such as transformers or circuit breakers, inasmuch as it has, when in liquid form, a dielectric strength comparable, or even superior to that of oil. Furthermore, it is not inflammable, and its products of decomposition do n at form explosive mixtures or gases that are liable to injure the apparatus; and finally it is lnert with respect to the materials of construction of the electric apparatus.

Although this singular combination of the properties, inherent in the material, would seem directly to invite its use as an insulating medium for electric apparatus, I am not aware that anyone has ever thought of using it for thi purpose, probably because, in distinction to oil, carbon tetrachloride, or other substances that have been tried in the past, diphenyl oxide is solid at room temperature, and melts under atmospheric pressure at about 27 C.

According to my invention, I overcome the difliculties which, heretofore, appeared to be present in the way of utilizing this substance as an insulating medium in transformers or circuit breakers, and deterred those working in the art from applying it to such apparatus, by utilizing the fact that electric apparatus is usually operated at such temperature that the surrounding medium is considerably above the melting temnerature'of diphenyl oxide. Accordingly, if diphenyl oxide is placed in an electric apparatus, which operates under a load, the heat dissipated by the apparatus will automatically maintain the diphenyl oxide in a state in which it will best perform its insulating functions, namely in the liquid state in which the other media, such as oil or carbon tetrachloride have been used heretofore.

In may cases, it is important that the insulating medium be maintained in liquid state, not only during the actual operation of the apparatus, when it is dissipating the losses incident to the flow of current through the apparatus, but also during the periods when the apparatus is not loaded.

According to the invention, I provide additional heating means for heating the diphenyl oxide so as to maintain it in the liquid state independently of whether the apparatus in which itis utilizedis loaded or not.

In the preferred arrangements of the invention, automatic means are provided for selectively cutting in or cut additional heater means utilized for maintaining the temperature of the diphenyl oxide at a value at which it will best perform its insulating and cooling functions.

In addition to the advantageous properties of diphenyl oxide pointed out above, it also has high heat conductivity which makes it in this respect much more desirable than the other available materials. The boiling point of diphenyl oxide, at atmospheric pressure, is around 260 (1, and is in this respect also more advantageous than the other media.

Another advantage of diphenyl oxide is the fact that the gases or vapors developed thereby are not noxious, as is the case with carbon tetrachloride, for instance.

An exemplification of the invention, as applied to circuit breaker, is shown in Figs. 1 and 2 of the drawings.

The circuit breaker comprises a tank 1, of iron or the like, having insulating lead bushings 2 mounted on the top thereof. The

amass? inner ends of the bushings carry main contact members 3, to which connection is made through lead wires 4, extending through the bushings to the exterior of the tank. The contact members 3 cooperate with a suitable contact brush 5, which is supported at the end of an insulating handle 5 by means of which the brush may be pulled upwardly for establishing the circuit, or downwardly to break the circuit.

Arcing contact members 7 are also provided in shunt to the contact surfaces between the brush and the contact members 3, in order to avoid arcing at the main contact surfaces when interrupting a current.

The tank is filled with diphenyl oxide up to a level above the operating parts of the circuit breaker, so that the electric operating parts are embedded in diphenyl oxide and the contacts between brush 5 and the contact members 3 of the circuit breakerv are broken thereunder.

The several parts of the circuit breaker are preferably so dimensioned that when normal current is flowing through the closed circuit breaker, the losses will develop enough heat to maintain the body of diphenyl oxide in liquid state. Under such conditions, the circuit breaker will operate within a liquid body of diphenyl oxide similarly as in oil, or other are quenching media, used heretofore. However, on account of the su perior properties of diphenyl oxide, a high degree of insulation and good cooling will be secured between the several parts without endangering the circuit breaker and the en tire plant, by reason of fires, gas explosions, excessive deterioration or the like, that occurred so often in oil-filled circuit breakers.

In order to maintain the body of diphenyl oxide in liquid state when the circuit breaker is open, or when less than normal load current is flowing therethrough, an additional heatmetallic strips, adapted to flex to the right to open the heating circuit, if the temperature of the liquid within the tank rises above apredetermined value,-sa for instance',---30 and to flex to the left to t e position shown to energize the heating coil 10, if the tempera:

ture of the diphenyl oxide approaches the freezing range.

In Fig. 2, I have shown a circuit diagram of the circuit breaker in Fig. 1, with addi tional heating coils for maintaining the diphenyl oxide in liquid state by current supplied directly from the line which is being controlled by the circuit breaker. The circuit breaker is shown to be of the doublepole type and is utilized, for instance, to connect a supply transformer 21, to a main transmission line 20.

In order to maintain the diphenyl oxide in liquid state, when the current through the circuit breaker is not sufiieient to heat it above the melting point, I provide two sets of heating coils 23 and 24, arranged to be connected between the leads of the incoming lines and of the outgoing lines, respectively.

Each set of heating coils may, for instance, comprise one heating coil 25, adapted to be connected by means of a temperature responsive switch 26 to the lead-in conductors of theincoming line and so arranged as to automatically energize the'heating coil, if the temperature of the diphenyl oxide fillin'g drops below a predetermined value, say 35 C. Should the conditions be such that the heat generated by the heating coil 25 is not suflicient to maintain the desired temperature, a second heating coil 27 is auto matically energized by means of another tem-' perature responsive switch 28', adjusted to act at a somewhatlower temperature than the switch 26 of the first-mentioned coil 25.

By providing a plurality of heating coils of the character described above, arranged to be energized by temperature responsive switching means that are actuated in a definite succession, I mayassure close control of the energy required to maintain the diphenyl oxide in the liquid state, or, in general, in the state in which it will best perform its insulating and cooling functions. 4.

The set of heating coils 24, which is connected between the lead wires of the outgoing line, may be arranged in the same manner as the set of coils 23 of the incoming line, as described above.

Through the provision of a separate set of heating coils 24, in the outgoing-line, the temperature of the circuit breaker filling is maintained at the desired value independently, whether the supply transformer 21 is under voltage or not, since, in most cases, the distribution line 20 will be maintained under voltage through a connection with another supply point of the system of which it is a part. p

In the preferred arrangement of my invention, the-temperature responsive devices which control the energization of the individual heating coils 23 and 24 are so arranged that, first, a heating coil connected between the incoming leads. is energized; then a heating coil that is connected between the outgoing lines is energized, etc. Fig. 3 shows my invention as applied t a transformer comprising a core 31 with windings 32 mounted in a tank 33 having lead-in connections 34 extending through bushings 35, mounted on the walls of thet-ank, The tank is filled with a body of diphenyl oxide which is preferably maintained in liquid form, as explained above.

The transformer may be so designed that the heating losses will, under normal operating conditions, maintain the diphenyl oxide in liquid state.

In the preferred arrangement, I so design the transformer that the losses, due to the magnetizing current, are sufiicient to maintain the temperature of'the body of diphenyl oxide adjacent to the transformer in molten condition. However, I may also provide a separate heating coil 36, as in the case ofthe circuit breaker, arranged-to be auto matically energized by means of' a heat-responsive switching device 37, to maintainthe body of diphenyl oxide within the tank at the temperature best suited for operatiom' WVhen utilizing the heat generated by the magnetizing current of the transformer for normally maintaining the diphenyl oxide'in liquid state, it will, in most cases, be sulficient to have only a part of the body diphenyl oxide in liquid form; namely, the part of ,the diphenyl oxide which is immediately adcore .and transdistributed within the tank that when'heating the apparatus, after it was for a time out of operation, and the diphenyl oxide is in solid state, the solid diphenyl oxide will only gradually be melted to avoid dangerousstresses that may develop bysudden and uneven expansion' of the solid body in the tank.

As an alternative to the use of substantially pure or unadulterated diphenyl oxide,

with auxiliary heating means for'maintaining it in liquid state, independently ofthe load and the losses in the apparatus, I may artificially lower the melting temperature by adding to it a substance that will cause the resulting compound to remain liquid within 1 a wider range of the operating temperatures than is the case with diphenyl oxide alone. I have found that chlorinated diphenyl oxide has such characteristics, and I, accordingl utilize the same when separate heating coi are to be avoided or are undesirable.

My invention is not restricted to the particular arrangements described hereinabove,

but is susceptible of many modifications which will suggest themselves to those skilled in the art. For instance, instead of diphenyl oxide, I may use. other diphenyl compounds zation of chlorinatedoil as an insulating me-' diurnfor circuit breakers, transformers and the like. Chlorinated oil is'not'infiammable and doesv not develop explosive mixtures to the same extent as ordinary oil used heretofore; and, on the other hand, it has substantially all the insulating qualities of pure oil. More generally, my invention is intended to embrace 'all'insulating liquids that have a dielectric strength of the order of oil, that is, of more than 100,000 volts per centimeter and, on the other hand, is not inflammable and does not develop explosive mixtures, and

, is inert with respect to the materials of construction of the apparatus.

Diphenyl oxide is also known as and sometimes referred to as phenoxybenzol, diphenyl ether, or phenyl ether.

I claim as my invention:

1. An electric circuit-breaker having interrupting contacts operating in a body of liquid diphenyl oxide.

2. In an electric-apparatus having conducting and insulating elements, an insulating medium comprising diphenyl oxide.

3. An electric apparatus comprising conducting elcment-s immersed in liquid diphenyl oxide. 7 4' 4. The combination withan electric apparatus comprising conducting elements and solid insulating elements for supporting and spacing said conducting elements, of a body of diphenyl oxide surrounding said apparatus for cooling and insulating'the same.

5. An electric apparatus comprising a vessel, a body of diphenyl oxide in said vessel, apair of conducting elements maintained at different potentials, solid insulating members for supporting and spacing said elements, said elements being lmmersed in the body of diphenyl oxide, and means for maintaining the diphenyloxide in liquid state irrespective of the flow of energy through said apparatus. Y

6. An electric apparatus comprising a ves sel, a. body of diphenyl oxide in said vessel, 8. pair of conducting elements maintained at diilerent potentials, solid insulating members for supporting arid spacing said elements, said elements being immersed in the body of diphenyl oxide, and means for maintaining the diphenyl oxide in liquid state irrespec e ea? 

